Telescopic shock absorber piston construction



INVENTOR. i'

2 Sheets-Sheet 1 Z?) y Z4 Feb- 9, 1954 H. L. cHlsHoLM, JR

TELESCOPIC SHOCK ABSORBER PISTON CONSTRUCTION Filed Jan. 8, 194'? Z9 Zi Feb- 9, 1954 H. L. cHlsHoLM, JR 2,668,604

TELESCOPIC SHOCK ABSORBER PISTON CONSTRUCTION Filed Jan. 8, 1947 2 Sheets-Sheet 2 Iig 7 /35 y2 uw @f5 /4/ ,/57,

/9 2d JNVENTOR. Hfzefr L (ms/mw; z/.

Jaym

Patented Feb. 9, 1954 '.TELESC'OIICSHOCK AESDRBERPISTON CLONSTRUCTION 2Harryf.L.Chisholm,`l;Ir., Buifalo,':'N.., assgxmrto iHoudailleeHersheyiCorporation,Detrcit,.MilL,

sa. AcorpolatiomofMichigan 10"6G1aims. T1 This fnventicnrrelatesto improvementsin di- '.'rect meting or ttlescopic 'shock absorbers, uand rmorezpart-cularly' tol shockflabsorbers ofl thisitype :wherein f-a lvalved'piston iis freciprocablyy sl-ida'ble witlmriarcylinder in the-presence of a`hydrau1ic Anfimpor-tantbjectfoff-this inventionis to1 provide *an limproved *direct =-acting hydraulic shock `absorlwer:Whichisfespecially-Well adaptedfor low 'roost masszproductionmetho'ds of'manu'facture but mevertheless=measures up A"to high performance :standards .Another objectfo'f `thelinventionresides inth'e provision :of fa direct 1'acting shock "absorber as- Lserbly fcomprising 'relatively few Aeasily "manu- Ia'cture'd parts'that areespecially-well adaptedifor highspeed:asserbly -HAT'fuI-ther'object''-'the?inVention resides in the provision :of :improved 'control valve means in a #direct actingfhyslraulic shock absorber.

Stillianotheribject 'of Vthe invention vis'to provdernovellvalve structure'in thel pistonv oratdirect :acting .rshock labsorber responsive to `respective compression` stroke fand reboundl stroke hydraulic spressures f inl the/operation or" theshock absorber.

Other-objects, features iand advantages of the A'present "invention lwill be readily apparent "from the .followin-gfdetailed description of 'c'ertainjprefe'rre'clfembddiments thereof` taken in conjunction lwitlr the" accompanyingtthree sheetsof drawings, 30

t2 :cerne'doperates on"-the-pincilleofihydralicluid Afresistance'Ito the reciprocationsWithin'facylinder off'ar'pistonlv'lific is'connetedf'to onedftwolrlaltively ^movable1parts, L'suh 'as the'sprung mass of 'avliclefwli'ile lithefcylinder isfccnnected `'to the f'other fo'f ltl'xe. relatively movable parts, Asuch las the-'unsprungmass of :the vehicle. tIn -sucha shock absorbrerithe compression-stroke-'of' thepis- Aton, v.While -l'resisted 5to fa# certain extent, is freer *than the'frebound 'stroke which is rcontrolled tto be substantiallylresisted'to occurlata s'l'owerra'te.

aA-shockfabsorberfconforrning i toi these requirelImentsf-and embodying 'an improved, simrfilied assembly including novelfand highlyeicientcontrol T`Valve means is -sh'own in *Figure l1. This shock 'absorber comprises a piston I5 4reciprocable Within af' cylinder IB and having-a piston roclfy I'I whicheztends' beyondlthe'rend ofthe' cylinider.' I'iy 'and carriesfat its outer'enfl suitable means "such as an eye I8"by'-vvhich it is adapted fto" be connected f to one 'of relatively movable J members such as an:automobileA chassis.

Concentric about the cylinder 'tube II iis a 'tuibul'ar 'reservoir -*casing -IQ 'of somewhat greater length fand 'having thelower end vthereof telescopeda'bout `-the rim of va Vcup-shapedbottom 'heacl 'or-'closure 'both thetubularcasing I@ and 'the head ZIIbeingformed from metal and secured together in luidtight relation as by 'means yof zweldingZ'I. Secured'tothey outer side'of theend closure'Ze-fas by'means of `Welding@ .is an l`eyeZ fby Whichthe'lower endv'of the shock absorb'eris adapted` to be 'connected to 'the Aremaining relatively movable meni'bersuch kvas 7 the axle structurefo'f a'vhicle"in=which='the shock absorberis installed '-To secureth'e -cylinder tub/e -15 rigidly Within f-the ssl-rock :absorber A' asse1'x1b1y, the 4top 4closure plug'f'Z 4i'isthreaded intoftheupperend o'f *the resffFigure Z3 isa ltransverse, sectional Vdetail view 40 Aervcnircasirig'fI!! and is'fformed Witha'dcwnwardly "Figuresfilisra fdiametral,""fragmentary, sectional fviewthrough armodifdform o'fgpistong Fi/gure 5is aidiarrietral,` sectional View through ialfurthermodiedform of piston;

"Figure L6 is a transverse 'sectional lan View "through the lower "end 'of the hydraulic .shock absorber taken-ssubstantially l' in then-lane uof" line .Wwll'liffigure "1 ;`-"and Figureff? is-afdiarnetral, fragnientary,- sectional @View takenssubstantiallyalong the'i line "VH-VH fdfffignref.

ffacing annular shoulder a215 lopposing the upper -fendof-thefeylinderJIS. Aownwardly'protru'ding axial boss 21 on the ,plug has its upperportion -cylindricaha'nd Vits'loWerportionformed with an asserriblweas'ing tapering 'circumference "2x8 .and dependsintothe'upperfendportioncfthe'cylinder I6 With-a vdiametralzrress nt to insure hydraulic sealandconcentricity. :Athread'sell carried inan annularfradially nutwarldly :opening ntermedi'ate'groovein the 4closureplugjlgprovides 'a luidtight jointbetweentheiplug'andthereservvo'irfcasing I9.

Atitsilowererr'd vthe .cylinler II Jbears against 'an annular; upwardlyjfacingstepped: shoulder 3 I the type with which the present invention is c011- 5'6 one lower Mclosuremember er footvalve casing 32 which is clamped thereby against the inside of the lower closure cup 2i). A properly selfcentered relationship of the closure member 32 with respect to the closure cup 29 is assured by an inwardly sloping annular herein substantially frusto-conical formation 33 of the inner wall of the closure cup 25 against Vwhich the lower edge of the closure member 32 shoulders, such lower edge being preferably formed with a complementary seating bevel 34. Thus, assembly of the shock absorber structure is substantially facilitated while at the same time manufacturing tolerances may be relatively large, the entire assembly being held together by the top closure f plug 24. The lcylinder I6, in the course of assembly, is substantially self-centering and with especial regard to the piston I5, the latter during the assembly operation being preferably disposed closely adjacent to the bottom of the cylinder I5 to assist in the attainment of concentricity.

Passage for the piston rod I1 is afforded through the closure plug 24 by an axial bore 35 therethrough. Leakage of hydraulic fluid out through the bore 55 or transportation of fluid beyond the bore by outward movement of the piston rod I1 is prevented by a packing gland unit 31 which is fitted within a concentric counterbore 33 in the outer end of the plug 24.

A head 39 carried by the outer extremity of the piston rod I1 has an annular shoulder 45 by which it is adapted to engage the outer end of the closure plug 24 as a limit stop upon extreme inward movement of the piston rod I1 and the piston I5. A shield tube 4I may be secured as by means of welding or the like to the `outer edge of the shoulder 4E! and surrounds the reservoir casing VI 9 in spaced concentric relation.

Outward transportation of hydraulic fluid by the piston rod I1 is further prevented by scraping off thereof in a groove 42 formed as a counterbore at the inner end of the piston bore and into which open radial pressure relief slots 42a. `An axially outwardly spaced fiuid trap and drainage channel 43 annularly formed in the bore 35 and draining by means of a lateral passage 44 into the top `of the reservoir space provided between the reservoir tube I9 and the cylinder I6 take care of such fluid as does travel out on the piston rod I1.

The piston I5 divides the space within the cylinder IE into an upper high pressure chamber 45 and a lower low pressure chamber 41. In service a relatively low order of resistance is afforded to downward or compression movement of the piston I 5 by hydraulic fluid which fills the chambers 45 and l1 while on the return or rebound stroke -of the piston a relatively high order of resistance is provided for. To this end the piston I5 is equipped with a valve system which will appropriately respond to hydraulic fluid pressures in the reciprocations of the piston to control the shock absorbing or damping function of the piston.

Accordingly, the piston I5 comprises a skirted, annular piston body 48 of an outside diameter to fit in close, sliding engagement with the inside surface of the cylinder I6 and of suflicient length .to obviate the need for any special sealing gasket between the cylindrical sliding interfaces of the piston and cylinder. The internal diameter of the piston body 48 is such as to adapt the same for sliding assembly with the inner terminal end portion of the piston rod I1. A retaining nut 49 is threaded onto the lower end portion of the piston rod I1 for securing the piston body 48' 4 place and has a lower portion extending axially downwardly beyond the end of the piston rod. Opposing the retaining nut 49 clampingly is means such as a split ring 50 seated in an annular, radially outwardly opening groove 5I in the piston rod.

For compression blowoff, the piston body 48 is provided with a plurality of hydraulic fluid passages 52 (Figures 2 and 3) which are disposed in a uniformly spaced series adjacent to the periphery of the pist-on body and extend axially between a chamber 53 dened by the skirted portion of the piston body and an annular, axially upwardly opening channel 54 in the upper shoulder of the piston body. Compression blowolf is normally restrained by a check valve structure 55 which in the present instance is preferably an outer marginally flange-reinforced flat ring disk of a diameter and width to seat sealingly on the shoulder of the piston body over the blowoff channel 54. Normal fluid sealing relation of the valve ring 55 is maintained by a relatively weak, radially fingered ring disk spring 51 bearing thereagainst and having an internal diameter to t about the piston rod I1. The spring 51 has a plurality of equally spaced, radially extending downwardly bowed spring fingers 58 engaging the outer margin of the valve 55. The fingers 58 are appropriately tensioned to afford the proper compression blowoif resistance to the check valve 55. Although, as seen in Figure 3, the piston is provided with six compression blowoff passages 52 and the check valve spring 51 with an equal number of the tensioned fingers 53 for uniformly opposing the check valve, the spring fingers and the passages 53 need not necessarily coincide but may be disposed in any haphazard rotative relationship, thus facilitating assembly by relieving the need for particular attention to this detail. The spring fingers 58 are of uniform length with the tips thereof adjacent to the marginal reinforcing flange of the check valve disk 55 for maintaining the check valve in substantial concentricity and in sealing relation to the blowoif channel 54.

Attachment of the spring 51 in properly spaced relation to the check valve disk 55 is effected by clamping the spring between a narrow flat spacer ring 59 closely encircling the piston rod I1 and bearing on the shoulder of the piston body 4B, and a retaining collar ring 50 engaging the upper side of the spring ring 51 and having an upper inside corner, rabbet groove 6I complementary to and receptive of the contiguous marginal portion of the split retaining ring 50. Thereby, the clamping action of the retaining nut 49 against the piston body 48 acts, through the piston body to drive the spacer 59, the ring 60 and the interposed spring ring 51 longitudinally clampingly against the split retaining ring 50. At the same time the ring 50 locks the split ring 59 against spreading, and leaving its retaining groove 5I.

In the compression stroke of the piston I5, flow of hydraulic fluid past the piston will be resisted with cushioning or shock absorbing effect by the check valve 55 under the influence of the spring 51 up to a predetermined rather low pressure, whereupon the spring fingers 58 yield and the check valve will unseat for compression blowoff of hydraulic fluid from the pressure chamber 41 through the piston chamber 53. the passages 52 and the blowoff channel 54 into the high pressure chamber 45. However, the valve 55 effectively checks return flow of hydraulic lll the rebound movement of the piston is. i

.samengaan Qontrol :of .':rbound rhydraulic luid row from theihigh'ipressurefehamber ltrpast .thexpiston its lirito :the low Yipressure hamber sill is .eie'eted :by fa walve structure .vvhich :is tpreferahly ronerative mithin :la relatively: large rdiameter faxial bore :62

un the iinn'er terminal fend portion tof the -pistofn amd Lvl Sand. :including ya :zblnwoi rcheck Naive :613. llihewivezisfpreferahlyeof:the piugztyperhaving ia :generally rfrusto-oonieal face i164 zengageable with Iia ivalve seat x65 provided ias @sa isholder at th-e xmouth :of aereducedfdiameter axialzupward :extension "61 of ithe axial-'valve rbore '462. Means for normally relatively :strongly-biasing the v.redmundblowoff-Nalve zhereinfcomprises:aastrongily loaded :coiled :compression 'spring l.68 driving #against .the ,flower shoulder Jof fthe :head :of `lfthe ivaivexfahoutaireduced diameterashanin thereof fandaxseated upon lan ntegralsspider fat 'the 'lowerfend fof gthe lretaining mut H49. The :tension 'of fthe fspring y58 =.is :predetermined "to .fhold `the rblowoff theek :valve 63 seated .in fopposition to :substantial zrebound :hydraulic xfluid'f pressure .ex- .'erted against the wvalve Within :the axial :bore rlrby wayfofa crossbore .f'H .openingthereinto through *fthe piston frod I1 fabove the "piston d5. In response zto predetermined rebound hydraulio .fluid lIzaressure theicheek -Nalve l15? .is adapted to #be iunseated, `as iis `indicated in `broken .outline in .Figure :2, in opposition :to the biasing .spring .highpressurefchamber'115 zpassesover .the -low gpressureehamber T411, flowing past the -yalve w63 .through =the bore 6 2 :and out through the -bore in fthefnut and ithroughi-thespider '15). Com-- Means tior iguiding the V@rebound blowoff .val-ve ;63- iorfreciprocalmovement. andtholding rthesame .substantially-concentric within the .bore 62 ;and

preventingcanting or transverse-:vibration*.thereof. comprisesm -,the 2,present instance.- aI guide .pin

'.or :rod 112 whichextends .in Yslidalole,guiding .rela-- tion axially through the valve 63 andahasiitsuplper r.extremity .or .tip twithin fa .reduced .diameter pilot .boreextension .1-3 iin the .=pistcn,.rod. ,The

iloweneXtremi-ty of the guide pin ,is .of .reduced .Means are .provided to ,accommodate .normal -resltrirnted .or :metered hydraulic fluid .displacementbetween the .chambersh and LAilito cushion .the .relatively llow .magnitude shock absorbing reciprocations of ,thepiston .f5 l.and Lto serve 1in .the mature .of .an .orice-bfore-.blowoi fior .preyliminary 'limite'dflow o'f .hydraulic iiui'd ,onboth `clompression and ,rebound .strokes .of the i.piston. "To 'this end, the valve guide pin "I2 is .flattened .to providea chordalfface l1 ,throughoutalongi- '.tudinal.exteritffromvvellbelowto well above the tarea ltherecf encompassed "by 'the 'valve 63 througih'out 'its reciprocal range 'df voperation whereby to provide a "free, 'metering "hydraulic Viiuid *passage 'b'yfpa'ssing the'yalve 63.

'.In :the .operation or the 4piston 11"/5, "therefore, :10W magnitude reciprocations .corresponding "to :comparatively 4slight or low Tmagnitude relative imovemen't df the .respective #movable .members 'to which the v-shock absorben is attached .are actheiat :.'Ifl ff the valvelguiiing zpin f72. `vvWhen the mompressinn stroke magnitude .hand .intensity :demandemompressiun blowoi 'through 1 the lpassages :"ifinithetpistonrandapast .thercheck .valver tends itu equalize :the ipressure in the :cylinder .iehamhersA-:zandee'l *.@nzreboundfactiongwherein the most important shock absorbing functioniio'f fthe i shriek absorber occurs, tequilizalti'oneof ipresvsureloetween .thenylindenchambers,avhengreater vpressure'develops:inthepressure:chambertdthan can be equalzed 'through :the :metering @orifice lattordedsby:the''.vz`il.ve guiding pingfiat r11, willbe rta'izen mare:A orf by iunseatingrof the reboundblow- :Gifmania-163. lyhaving' the effective fcompression blowoffivalvesiandarebound i blovvoii valves E5 Brand 1.753 1 respectively, aproperlyfbiase'd for '.theirsrespec- 'tive lfunctions .With `-regard, fof bourse, ato :the springingfan'dwegihtfof :the wehiele in .whichfthe #snoek fabsorber .unitis .installed excellent :triding qualities by .use f'of the :shock absorber l are L atitained even ftnoug'h the uvalve structure rand Lt'he eompressionfand '.reboundihydraulic uid'iiow :or "equali'zingsystem U'ffthefpiston,lareffrafrelatively simple-dnaraoter.

While fthe `fpiston f iin .ser-vice :normally :assumes approximately the position indicated 'iin "broken foutline iin Figure \1, 'and iin Ethe fextreme Aeompression Lstrdke :assumes the AvTull: outline -position o'ffigure l'aslimite'd bylthefheadtfthe -Iextreme irebound@strek-e .may fpro'ceedtofengagesmentstf the"'retai1iing'ringt50 Vfwithftheinnerfend of the #lesure plug boss Z27. @In fthe 'latter position; rebound fluid lbloek:.on-passage ofltheftransverse rports I mitwar'diy-past the f tip of the'fboss 'is avoidedlby the eountebore 42 and vvthe vrelief slots 42a.

A further Yii'rnpoi-i'fat attribute v"of @the piston structure i I'resides inthe lowfcost'atwhich the same 'may 1be'fmanufaetui-ed Wh-le-at the tsame time 7attaining a thigh -Adegree fof voperating: --eiIiciecy. AS toth'isth'e i1niforml-y-eylindrical'nature of `the jpiston rod fl l contributes i'e'iecti-vel-y since it 'can ibe v'-linis'he'd l"on "a eenterless lgrinder linsteadfoferneuter grinder and therebyaequires aihigfh degree offconcentrieity:Whi'ehis'fhighly" important for-operating`con-centricityof the Y piston 5F55 ina the ylinderi F6 In the modified `'alternate "form of lpiston -la shown in Figure 4 simplification-land reduction in number of"componentpartsihasbeen attained. LIn' this iform, ,a ,Skirted ,piston "body "175 is' slidably assembled *about the1piston' rod :We and `retained "by a nut *T9 'threaded lonto `'the inner extremity Gfthe-pis'tonrod.

From a "Chamber 85.1 'de'ned'within the 'skirt 'portion of 'the piston tbody T8 hydraulic 'fluid is afdaptedptojpassor compression'relief or iblowoff 'through :a :series Afof `axially VextendingV hydraulic cfluid jjpassages "8l `which lead "into "an annular, axially 'upwardly opening jgroove 'or channel "82 in'a stenpedshoulderB-S o'ftheuppeiside of the valve "body providing a annular seatffor a .flat fdisk ring. checkvalve'fi :which `normally `lies in sealing relation Lto the compression blowof Ac`ii1am1el2. The heekyalve't is maintained .coneentriciby an upwardlyprojecting hulb 5 .in- -tegral vviththe pistonhodvdand otsuchiheight as to .clamp a lfiat, `disk ring type s pringdl in normally .Spaczed relationto the :check .valve 84 and against a'bac'king 1ing`-33whieh inturnis seatedandclarnped "against -an opposingn'etainvin@r shoulder "39 ionJ the piston rod. A -`series 'df uniformly 'radially :extending and 'downwardly .bowedi'lowltension springngers 250 onthe `'biascommodated 'by the vley-pass orifice provided by *75 'ingspringB'l extenddownwardlywithimthespace 7 provided between the top of the check valve 84 and the opposing face of the backing ring 88 and act normally to hold the valve ring 84 on its seat. The tension of the spring fingers 90 is prop- 'erly calculated to afford the desired degree of low compression blowoff resistancelfor the check valve 84.

Low magnitude and preliminary hydraulic fluid displacement in both directions is provided for by having the check valve 84 formed with a uniform series of small bleed orifices 9 I.

For rebound equalizing hydraulic fluid blowoi, the piston rod Ila is formed with a cross bore 92 above the piston in communication with an axial uid passage bore 93 which in turn communicates with or forms an axial continuation of a lower end axial counterbore 94 of larger diameter in the piston rod. Compression fluid flow is entirely blocked and rebound blowoi is resisted to a predetermined value through the iiuid passages 92, 93, 94 through the piston rod by a plug type check valve 95 having the seating face thereof substantially frusto-concal and sealingly engaging with a valve seat 91 provided as an axially inwardly facing shoulder at the inner end of the counterbore 94.

An axial guide for the valve 95 is provided by a cylindrical guide pin 98 having the lower end thereof of reduced diameter to provide a securing boss 99 preferably xedly assembled with an integral spider at the lower end of the nut 19 and extending slidably through the valve 95. The upper end of the pin 98 ts concentrically slidably within a pilot bore upward extension I0! of the fluid passage bore 93. The relationship 'of the valve 95 to the guide pin 98 is such that while the valve is permitted to reciprocate freely between fully seated and unseated positions, as shown in full and broken lines respectively, it is held constantly against lateral movement and thus is free from canting or chatter which might otherwise develop in service.

A preferred degree of relatively strong spring bias is afforded for rebound blowoff check valve 95 by means such as a coiled compression spring |02 held in substantially concentric relation about the guide pin 98 and bearing at its upper end against the valve 95 and at its lower end against the spider |00.

In a further modified alternative form of piston |517, as shown in Figure 5, a skirted cylindrical annular piston body |03 is carried by a piston rod |04 which for this purpose is provided with a reduced diameter lower stem extremity |05 onto which is threaded a retaining nut |01.

In the piston b, provision is made for both compression blowoff and rebound blowofl` hydraulic fluid passage -directly through the piston body |03. To this end the piston body is formed with an axially extending outer, annularly spaced series of compression blowofi' passages |08 and with an inner, annular series of generally axially and preferably slightly radially downwardly and inwardly extending rebound blowo passages |09, both of which series of passages communicate through the top of the piston body |03 with a chamber I I0 within the lower skirted portion of the piston body. Y

The compression blowoff passages |08 communicate at their upper ends with an annular, axially upwardly opening channel |II which is normally sealed against rebound hydraulic fluid flow by a check valve disk or ring I|2 which is held substantially concentric by an axially upwardly extending spacer hub |I3 integral with 'the piston body. YThe hub |l3'bears 'against a. backing disk or ring ||4 seated against a shoulder |I5 at the lower end of the larger diameter portion of the piston rod |04 and confines under predetermined compression a disk or ring type of biasing ring II'I having a radially extending series of downwardly bowed spring ngers IIB bearing against the top of the check valve II2 normally to hold it seated. Upon compression blowoif, hydraulic fluid working against the check valve I I2 from the channel I acts to unseat the valve in opposition to the spring fingers |I8 as indicated in broken outline.

Rebound pressure relief or blowol through the passages |09 take place through openings ||9 in the check valve disk |I2 and a shallow axially upwardly opening groove |20 in the top of the piston body |03 at the entry endsof the passages |09. For improved rebound fluid flow to the openings |I9, the spring backing plate or ring |I4 may be formed with appropriate iiow passages I2I. At'their discharge ends the rebound passages I09 open into an annular downwardly opening axial chamber |22 with which registers an annular, rabbet groove |23 inthe upper, outer edge of the retaining nut |01.

Blowoff hydraulic fluid through the registering channel |22 and groove |23 is vblocked or checked by a valve member |24 which is in the form of a sleeve slidable on a cylindrical guide surface |25 provided therefor on the nut |01. Means such as a coiled compression spring |21 normally biases the valve member |24 into sealing relation wherein the upper sealing edge, identified at |28, bears sealingly against the valve body |03 about the outer margin defining the channel |22. For this purpose'Lthe spring |21 encircles the valve member |24 and bears against a downwardly facing radial shoulder |29 adjacent to the upper end of the valve member, while the lower end of the spring seats on a lateral flange |30 integral with the lower end of the nut |01.

To render the valve member |24 responsive to blowoff hydraulic fluid pressure, the radially inner marginal portion of the axially upwardly directed valve face |28 is annularly exposed to the blowoi fluid pressure within the channel |22. As a result, when sufiicient rebound blowoff pressure has developed to act upon the exposed annular portion of the valve face |28 to overcome the bias of the spring |21, the valve member |24 will slide open, as indicated in broken outline, and afford a pressure relief opening from the channel |22 and the groove |23 into the piston chamber I I0 which is freely open below the piston. To facilitate fluid flow thereby with a minimum of agitation, the head end of the valve-member |24 is preferably beveled, as indicated at |3I, from the valve face |28.

Since in the reciprocations of the piston within the cylinder of the shock absorber unit provision must be made for the volumetric displacement of the piston rod, the space between the cylinder I6 and the surrounding reservoir casing I9 is utilized as a piston rod displacement reservoir or replenishment chamber |32 which hasno direct communication with the high pressure chamber 45 but does have communication with the low pressure chamber 41 through a foot valve structure |33 (Figures 6 and 7) associated with casing 32. To this end, the casing 32 is formed with an axial displacement bore or port |34 of substantial diameter opening at its upper end into an enlarged diameter counterbore |35 land end portion of the piston rod, shoulder means on Vthe piston rod, a nut member threaded onto the extremity of the piston rod and clamping the piston body in place with respect to said shoulder means, a fluid passage through the piston rod bypassing the piston and opening axially through said extremity, a guide rod supported by said nut and extending into said passage, and a valve member slidable on said guide rod and controlling the ow of uid through said passage.

2. In combination in a direct acting shock absorber, a piston and piston rod assembly including a piston body slidably received on the end portion of the piston rod, shoulder means on the piston rod, a nut member threaded onto the extremity of the piston rod and clamping the piston body in place with respect to said shoulder means, a fluid passage through the piston rod, a guide rod supported by said nut, and a Valve member slidable on said guide rod and controlling the flow of fluid through said passage, said valve member and said guide rod having a restricted bleed passage therebetween.

3. In combination in a direct acting shock absorber construction, a piston structure including a piston rod having an axial fluid passage bore in its extremity portion and a cross bore communicating with the inner end portion of said fluid passage bore, an annular groove in said rod below said cross bore, a split ring shoulder member in said groove, a valve body slidably received on the extremity portion of the piston rod, a retaining nut threaded onto the extremity portion of the rod and retaining the valve body between its adjacent contiguous face and said shoulder member, said nut having a spider thereon carrying a guide rod extending axially through said bore, and a valve slidable on said rod and controlling the ow of fluid through said bore.

4. In a direct acting hydraulic shock absorber construction, a piston operable in a cylinder for dividing the cylinder into high pressure and low pressure chambers, a piston rod on the piston formed with a rebound blow-off fluid passage therethrough including an axial bore in the piston rod, a smaller diameter stem extending axially through said axial bore, a Valve slidable on said stem and normally biased into sealing relation to said passage, and means for compression blow-on, said stem having continuously open leed passage in the periphery thereof b-y-passing said valve.

5. In combination in a direct acting hydraulic shock absorber construction, a cylinder, a piston reciprocable in said cylinder and dividing the same into high and low pressure chambers, a piston rod carrying the piston, an axial bore in the end of the piston rod extending to the high pressure side of the piston and having passage therefrom communicating through the piston rod to the high pressure chamber, a smaller diameter stem extending axially through said axial bore, and a rebound blow-oir valve slidable on said stem and normally biased into sealing relation to said passage, said axial bore having a reduced diameter shoulder intermediate the ends thereof affording a seat for said rebound blowoft valve.

6. In combination in a direct acting shock absorber construction, a piston assembly including a rod, said rod having an axial fluid passage bore through an extremity portion thereof and lateral openings from said bore spaced substantially from the end of said extremity portion, shoulder means on said rod at the side of said openings nearest the rod extremity, a piston member slidably engaged on the rod extremity portion, said piston member being of generally inverted cupshape and having uid displacement ports adjacent its periphery extending in generally axiall direction and a skirt extending substantially beyond said ports in the opposite direction from said shoulder means, Valve means for controlling uid displacement through said ports, a nut member threaded onto the extremity portion of the rod member and clamping said piston member against said shoulder means, said nut being of substantially smaller diameter than the internal diameter of said skirt to afford clear passage about the nut within sai-d skirt communicating with said. ports, said nut being hollow. and having spider structure at its end remote from the piston member, a stem carried by said spider and projecting into said rod bore, a valve member carried by said stem, and spring biasing means normally biasing said valve member into closing relation to said rod bore.

7. In combination in a direct acting shock absorber construction, a piston and piston rod assembly comprising a piston rod having an extremity portion with an axial bore therein and lateral passages into said bore spaced substantially from the end of said extremity portion, shoulder means on said rodgextremity portion, a piston body slidably mounted on said extremity portion, said bore having an annular shoulder seat therein, and valve means for controlling displacement of iiuid through said bore including a cylindrical guide stem and a spring biased valve member of annular form and substantiah length slidably guided by said stem and having4 a frustoconical face sealingly engaging said an? nular seat.

8. In combination in a telescopic shock absorber construction, a piston rod and piston assembly comprising, in combination, a piston rod having an elongated fluid displacement bore opening through one end thereof, said rod having at least one lateral passage leading to said bore; spaced substantially from said one end, a reduced diameter shoulder Within said bore adjacent toY said lateral passage and spaced substantially from said one end, a piston body carried by said rod and externally fastened thereto between said lateral passage and said one end, means associated with said rod and piston body and carrying a stem of smaller diameter than said bore,

said stem projecting intovsaid bore past said shoulder, and a valve member slidably mounted on said stem and engaging said shoulder-in fluid sealing relation, said valve member being of smaller outer diameter than the diameter of the rod bore in the portion of the rod bore between said shoulder and said rod end.

9. In combination in a telescopic'shock absorber construction of the character described,Y a piston rod, a piston mounted on one end portion of the rod, said rod end portion having an axial bore therein and at least one lateral opening from the bore beyond said piston, a valve seat shoulder in said bore, means associated with s said piston and rod and supporting a Valve stem of smaller diameter than saidA bore, said stemk 'extending entirely through said bore and into a pilot bore extension of said bore inwardly beyond 1 said lateral opening, and a valve member slidably carried by said stem and seating against said valve seat shoulder. Y Y 10. In combination in a telescopic shock absorber assembly of the Vcharacter described, a

13 piston rod, a piston carried by one end portion of the rod, a longitudinally extending fluid displacement bore in said piston rod opening through said end portion, means associated with said piston and rod and supporting a valve stem extending into said bore, said bore having an annular valve seat shoulder, and a valve meinber slidably carried by said stern and seating on said shoulder, said valve stem having a shoulder spaced from said valve seat shoulder and limiting unseating movement of the valve member from said shoulder.

HARRY L. CHISHOLM, J R.

Name Date Beecher Sept. 30, 1941 Number Re. 21,908

Number Number Name Date Wright Nov. 9, 1915 Chadwick June 12, 1917 Cushing Jan. 3, 1922 Anthony Dec. 14, 1926 Standlee July 2, 1929 Elsey May 19, 1931 Beecher Nov. 18, 1941 Read et al. Apr. 11, 1944 Whisler Aug. 8, 1944 Rossman July 3, 1945 Beecher Feb, 5, 1946 Beecher Mar. 12, 1946 Whisler Nov. 5, 1946 Cuskie Sept. 6, 1949 FOREIGN PATENTS Country Date Germany Aug. 19, 1921 

